Differential transformer flux valve



June 23, 1970 J. A. MEAD DIFFERENTIAL TRANSFORMER FLUX VALVE 2 Sheets-$heet 1 Filed Sept. 11, 1968 POWER SOURCE DETECTOR H6. 3 INVENTOR;

JOHN A. MEAD &

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June 23, 1970 J, A. MEAD 3,517,362

DIFFERENTIAL TRANSFORMER FLUX VALVE Filed Sept. 11, 1968 2 Sheets-Sheet 2 INVENTOR: 2 27 Joy/v A. MEAD &

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3,517,362 DIFFERENTIAL TRANSFORMER FLUX VALVE John A. Mead, 9140 Lawler Ave., Skokie, Ill. 60076 Filed Sept. 11, 1968, Ser. No. 759,029 Int. Cl. H01f 21/06 Claims US. Cl. 336135 ABSTRACT OF THE DISCLOSURE OBJECTS The subject device transforms motion of an armature into an A.C. electrical signal whose phase depends on direction of displacement from a reference or null position and whose amplitude is proportional to the amount of that displacement. Magnetic flux emanating from a centrally located primary winding couples selectively with two adjacent secondaries through specially shaped pole pieces in the stator and in the armature.

A primary object of this invention is to develop a variable dilferential transformer wherein all parts, including three windings, are coaxially disposed and there is no Winding on the movable armature. A further object is to provide a construction wherein armature movement gates a flux coupling the primary turns with two secondaries by means of rapidly changing fiux passage areas between the stator and armature pole pieces wherever they interface radially. A further object is to provide a trans ducer which is as small as any of its kind commercially available and whose sensitivity is at least an order of magnitude greater. A final object is to provide a construction which will serve as a device with forcing means as well as a signal generator.

SUMMARY OF THE INVENTION The present invention relates to a magnetic motion transducer having flux paths so arranged that there is a relatively high electrical response with relatively little motion.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross section of an embodiment for responding to linear motion;

FIG. 2 is an end elevation of the embodiment of FIG. 1 partially broken away;

FIG. 3 is a schematic diagram showing a typical arrangement for connecting the coils of the embodiment of FIG. 1;

FIG. 4 delineates flux paths in the device shown in FIG. 1 at the null position;

FIG. 5 delineates flux paths in the device shown in FIG. 1 with armature displaced to the right; and

FIG. 6 is an isometric cutaway of the rotary embodiment.

DESCRIPTION OF THE SPECIFIC EMBODIMENT Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief aid toward this purpose; as it is these that meet the requirement of pointing out the parts, improve ments, or combinations in which the inventive concepts are found.

Referring to FIG. 1, primary coil 1 and secondary coils 2 and 3 are wound on annular bobbins as typified by 4. They are surrounded on their sides by four paramagnetic stator pole pieces 5, 6, 7 and -8. Shaft 9 is free to slide linearly within guide jewels 10- and 11 which are mounted in holders 12 and 13 constrained by housing 14. Shaft 9 is fitted with an armature or flux carrying paramagnetic section which includes two spoolshaped bosses 15 and 16 centrally connected.

Referring to FIGS. 1, 2 and 4 flux emanating from primary 1 has a path F1 with respect to secondary 2. Path F1 can be traced radially and outwardly through pole piece 7, axially and to the left through paramagnetic coupling or barrel 17, radially and inwardly through pole piece 5, across the air gap 18 to the left end of spool 15, axially and to the right to the left end of spool 16, and then across the air gap 18 back to pole piece 7. Similarly, the primary flux also has a path F2 through secondary 3 by way of pole piece 6, barrel 17, pole piece 8, gap 18, through the right ends of spools 16 and 15 back to pole piece 6.

FIG. 4 depicts the armature centrally located being overlapped by stator poles 5, 6, 7 and 8 to their halfway point at both ends of spool 15 and at both ends of spool 16. In this armature null position flux from primary 1 couples equally with secondary 2 and secondary 3, i.e. the permeability of paths F1 and F2 are equal for all practical purposes. When secondaries 2 and 3 are connected in series opposition, as shown in FIG. 3, there is no net signal output at detector 35 since the voltages produced therein are 180 out of phase and are equal in strength. However, when shaft 9 is displaced from this null position, for instance to the right as shown in FIG. 5, flux path F1 becomes a longer, stretched path With more air while flux path F2 has consolidated its flux gates with more iron area in its air gaps. The absolute permeability of path F2 is increased while the permeability of path F1 is decreased. A signal will appear at detector 35. The output signal is the result of two factors, namely, (1) the increased voltage induced in secondary 3 because of the increased coupling, and (2) the reduced voltage induced in secondary 2 because of the reduced coupling. Since these two voltages are 180 apart in phase, the direction that the armature has moved can be determined by detector 35 by reason of the phase of the output signal as compared to the phase of power source 36 applied to primary 1. The signal producing change in iron area at the air gap occurs simultaneously at the four flux path interfaces defined by stator pole pieces 5, 6, 7 and 8.

Coils leads are dressed through slots in the stator pole pieces and soldered to five terminals, as typified by 19 in FIG. 1 and FIG. 2. Flux carrying pieces should be of a material that is known to have good permeability such as SAElOlO soft or Armco ingot iron. These pieces are shown in FIG. 1 as 5, 6, 7, =8, 15, 16 and 17.

Sensitivity may be increased by reducing the thickness (axial length) of the stator poles so that full flux coupling occurs with a lesser displacement. A model has been built and extensively tested. It demonstrates a specific sensitivity of volts per inch per volt excitation as compared with 3.0 for a standard commercial unit of the same size. This model has an overall length of 0.725 inch and outside diameter of about 0.312 inch.

In the rotary embodiment shown in FIG. 6 primary winding 20 and secondary windings 21 and 22 are also disposed coaxial with the longitudinal axis of the device. The four stator pole pieces 23, 24, 25 and 26 which surround the three windings are internally scalloped forming a plurality of angularly spaced individual pole faces or lands 27 and 27. The lands 27 for stator pole pieces 23 and 25 are oriented in line longitudinally and staggered from the lands 27 for pole pieces 24 and 26. The armature 28 is formed with the same number of longitudinal ridges forming salient poles 29.

When the poles 29 are rotationally oriented midway between the lands 27 of pole pieces 23 and 25 and thus also midway between the lands 27' of pole pieces 24 and 26, typical flux paths F1 and F2 may be traced in the same manner as described in detail for FIG. 4. Flux paths F1 and F2 will be of equal absolute permeability. There will likewise be equal flux coupling primary 20 with secondary 21 and with secondary 22. With the secondaries connected as illustrated with respect to FIG. 3, there will be no net signal output for this null position. When armature 28 is rotated from the centered position, for instance clockwise, its poles 29 will overlap more with the lands 27 of pole pieces 24 and 26 and less with the lands 27 of pole pieces 23 and 25. Thus, more iron area is caused to interface at the air gap at pole pieces 24 and 26 for the flux path of secondary 22 and less area at pole pieces 23 and 25 for the flux path of secondary 21. Accordingly, a signal output will appear at the detector 35 as depicted in FIG. 3 whose phase favors the dominant voltage now induced into winding 22.

Sensitivity may be improved by increasing the number of lands in the stator pole pieces and correspondingly the number of co-operating rotor poles without affecting coil winding requirements.

Flux in this device travels axially through the instrument in preparation for selective treatment for signal producing flux change in the air gap. In prior art such as ,the Microsyn these return paths are circumferential requiring a radially disposed coil at each pole. The construction is greatly simplified.

The subject construction lends itself to usage as a static forcing device. The linear embodiment of FIG. 1 may be used thus if primary 1 is constantly energized. When, in addition, only secondary 3 is energized, there is a force coercing the armature toward alignment with stator poles 6 and 8 and thus to the right. If only secondary 2 is energized in addition to the primary, the force is in the opposite direction. This kind of transducer is used in a force balance system such as an accelerometer. The rotary embodiment of FIG. 6 may be used as a static torquer if primary 20 is constantly energized. When, in addition, only secondary 22 is energized, there is a force coercing armature 29 toward alignment with the lands of stator pole pieces 24 and 26 and thus clockwise. When only secondary 21 is energized, the force is in the opposite direction. This device may be used as a torque generator such as those which are mounted on the gimbal axes of gyroscopes to induce precession. The exciting power for these force generating devices may be D0. or in-phase A.C.

Alternative embodiments may include a plurality of primary coils. In that event a secondary coil is positioned each side of each of the primaries, with poles pieces there between, in the same manner as is illustrated with respect to FIGS. 1 or 6.

I claim:

1. In an apparatus of the type described adapted to be connected to an alternating current source and comprising a stator member and an armature member with one of the members being movable along a given course with respect to the other member, the improvement comprising:

said armature member being formed about an axis and including first paramagnetic means defining a central portion with a plurality of discrete segments extending outwardly from said central portion, said segments being elongated in the axial direction having a predetermined width as measured along said course, said armature member being rotatable about said axis; and said stator member including two annular secondary coils coaxial with said armature, an annular primary coil coaxial with said armature and positioned between said secondary coils, whereby when said primary is connected to said source there will be a first magnetic flux linking the primary and one secondary and a second magnetic flux linkin said primary and the other secondary, and second paramagnetic means including annular pole pieces positioned at each side of each of said secondary coils and coaxial with said armature, said second paramagnetic means being positioned with respect to said first paramagnetic means that with said armature in a null position with respect to said stator said two fluxes have paths of approximately equal absolute permeabilities, with said armature displaced in said course on direction from said null position the path of one flux has an absolute permeability sub stantially greater than the absolute permeability of the path of the other flux, and with said armature displaced in said course the other direction from said null position the path of the other flux has an absolute permeability substantially greater than the absolute permeability of the path of the one flux. 2. In an apparatus as set forth in claim 1, wherein at least a portion of the path of said first flux is through a first group comprising the pole piece on the outside of said one secondary and the pole piece between the other secondary and the primary, and at least a portion of the path of said second flux is through a second group comprising the pole piece on the outside of said other secondary and the pole piece between the one secondary and the primary, and wherein the pole pieces of the second paramagnetic means each define pole faces, said pole faces being positioned so that at said null position the pole faces of one group approximately half overlap segments in one direction along said course and the pole faces of the other group approximately half overlap segments in the other direction along said course.

3. In an apparatus as set forth in claim 2 for use with detector means for determining a voltage output and its phase in relation to the phase of said source, wherein said secondary coils are connected in series opposition and adapted to be connected to said detector means.

4. In an apparatus as set forth in claim 2 for use with electric power means, and including means to connect said secondaries to said electric power means.

5. In an apparatus of the type described comprising a stator device and an armature device With one of said devices being rotatable about an axis with respect to the other member, the improvement comprising said stator device including:

two pair of paramagnetic members of generally annular configuration with an inside and an outside and positioned coaxially with said axis, said members being spaced from each other with one member of each pair being between the two members of the other pair respectively and defining three spaces between the four members, said members each having pole faces extending from one of said sides at spaced radial positions about said axis, the pole faces of one pair being staggered about said axis with respect to the pole faces of the other pair, three annular electrical windings, each winging being positioned in a respective one of said spaces and coaxial with said axis, and an annular paramagnetic barrel coaxial with said axis and positioned at the other of said sides of said members; and said armature device comprising:

a paramagnetic part, circular in cross-section and elongated axially, said part being positioned coaxially with said axis and extending from one end member to the other end member, said part having ridges extending the. length thereof and separated by grooves, said ridges being adjacent said pole faces and separated therefrom by a small gap;

whereby the magnetic flux .path for a winding in an end space includes a path which extends from the first member at the outside end of that space, across the gap between the pole faces of said first member and the ridges 1 the armature to the pole faces of said second member, through the second member, and through the barrel back to said first member.

5 THOMAS J.

References Cited UNITED STATES PATENTS KOZMA, Primary Examiner US. Cl. X.R. 

